/*
 * trace irqs off critical timings
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
 *
 * From code in the latency_tracer, that is:
 *
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 William Lee Irwin III
 */
#include <linux/kallsyms.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/fs.h>

#include "trace.h"

static struct trace_array               *irqsoff_trace __read_mostly;
static int                              tracer_enabled __read_mostly;

static DEFINE_PER_CPU(int, tracing_cpu);

static DEFINE_SPINLOCK(max_trace_lock);

enum {
        TRACER_IRQS_OFF         = (1 << 1),
        TRACER_PREEMPT_OFF      = (1 << 2),
};

static int trace_type __read_mostly;

static int save_lat_flag;

#ifdef CONFIG_PREEMPT_TRACER
static inline int
preempt_trace(void)
{
        return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
}
#else
# define preempt_trace() (0)
#endif

#ifdef CONFIG_IRQSOFF_TRACER
static inline int
irq_trace(void)
{
        return ((trace_type & TRACER_IRQS_OFF) &&
                irqs_disabled());
}
#else
# define irq_trace() (0)
#endif

/*
 * Sequence count - we record it when starting a measurement and
 * skip the latency if the sequence has changed - some other section
 * did a maximum and could disturb our measurement with serial console
 * printouts, etc. Truly coinciding maximum latencies should be rare
 * and what happens together happens separately as well, so this doesnt
 * decrease the validity of the maximum found:
 */
static __cacheline_aligned_in_smp       unsigned long max_sequence;

#ifdef CONFIG_FUNCTION_TRACER
/*
 * irqsoff uses its own tracer function to keep the overhead down:
 */
static void
irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
{
        struct trace_array *tr = irqsoff_trace;
        struct trace_array_cpu *data;
        unsigned long flags;
        long disabled;
        int cpu;

        /*
         * Does not matter if we preempt. We test the flags
         * afterward, to see if irqs are disabled or not.
         * If we preempt and get a false positive, the flags
         * test will fail.
         */
        cpu = raw_smp_processor_id();
        if (likely(!per_cpu(tracing_cpu, cpu)))
                return;

        local_save_flags(flags);
        /* slight chance to get a false positive on tracing_cpu */
        if (!irqs_disabled_flags(flags))
                return;

        data = tr->data[cpu];
        disabled = atomic_inc_return(&data->disabled);

        if (likely(disabled == 1))
                trace_function(tr, ip, parent_ip, flags, preempt_count());

        atomic_dec(&data->disabled);
}

static struct ftrace_ops trace_ops __read_mostly =
{
        .func = irqsoff_tracer_call,
};
#endif /* CONFIG_FUNCTION_TRACER */

/*
 * Should this new latency be reported/recorded?
 */
static int report_latency(cycle_t delta)
{
        if (tracing_thresh) {
                if (delta < tracing_thresh)
                        return 0;
        } else {
                if (delta <= tracing_max_latency)
                        return 0;
        }
        return 1;
}

static void
check_critical_timing(struct trace_array *tr,
                      struct trace_array_cpu *data,
                      unsigned long parent_ip,
                      int cpu)
{
        cycle_t T0, T1, delta;
        unsigned long flags;
        int pc;

        T0 = data->preempt_timestamp;
        T1 = ftrace_now(cpu);
        delta = T1-T0;

        local_save_flags(flags);

        pc = preempt_count();

        if (!report_latency(delta))
                goto out;

        spin_lock_irqsave(&max_trace_lock, flags);

        /* check if we are still the max latency */
        if (!report_latency(delta))
                goto out_unlock;

        trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);

        if (data->critical_sequence != max_sequence)
                goto out_unlock;

        data->critical_end = parent_ip;

        if (likely(!is_tracing_stopped())) {
                tracing_max_latency = delta;
                update_max_tr_single(tr, current, cpu);
        }

        max_sequence++;

out_unlock:
        spin_unlock_irqrestore(&max_trace_lock, flags);

out:
        data->critical_sequence = max_sequence;
        data->preempt_timestamp = ftrace_now(cpu);
        trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
}

static inline void
start_critical_timing(unsigned long ip, unsigned long parent_ip)
{
        int cpu;
        struct trace_array *tr = irqsoff_trace;
        struct trace_array_cpu *data;
        unsigned long flags;

        if (likely(!tracer_enabled))
                return;

        cpu = raw_smp_processor_id();

        if (per_cpu(tracing_cpu, cpu))
                return;

        data = tr->data[cpu];

        if (unlikely(!data) || atomic_read(&data->disabled))
                return;

        atomic_inc(&data->disabled);

        data->critical_sequence = max_sequence;
        data->preempt_timestamp = ftrace_now(cpu);
        data->critical_start = parent_ip ? : ip;

        local_save_flags(flags);

        trace_function(tr, ip, parent_ip, flags, preempt_count());

        per_cpu(tracing_cpu, cpu) = 1;

        atomic_dec(&data->disabled);
}

static inline void
stop_critical_timing(unsigned long ip, unsigned long parent_ip)
{
        int cpu;
        struct trace_array *tr = irqsoff_trace;
        struct trace_array_cpu *data;
        unsigned long flags;

        cpu = raw_smp_processor_id();
        /* Always clear the tracing cpu on stopping the trace */
        if (unlikely(per_cpu(tracing_cpu, cpu)))
                per_cpu(tracing_cpu, cpu) = 0;
        else
                return;

        if (!tracer_enabled)
                return;

        data = tr->data[cpu];

        if (unlikely(!data) ||
            !data->critical_start || atomic_read(&data->disabled))
                return;

        atomic_inc(&data->disabled);

        local_save_flags(flags);
        trace_function(tr, ip, parent_ip, flags, preempt_count());
        check_critical_timing(tr, data, parent_ip ? : ip, cpu);
        data->critical_start = 0;
        atomic_dec(&data->disabled);
}

/* start and stop critical timings used to for stoppage (in idle) */
void start_critical_timings(void)
{
        if (preempt_trace() || irq_trace())
                start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL_GPL(start_critical_timings);

void stop_critical_timings(void)
{
        if (preempt_trace() || irq_trace())
                stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL_GPL(stop_critical_timings);

#ifdef CONFIG_IRQSOFF_TRACER
#ifdef CONFIG_PROVE_LOCKING
void time_hardirqs_on(unsigned long a0, unsigned long a1)
{
        if (!preempt_trace() && irq_trace())
                stop_critical_timing(a0, a1);
}

void time_hardirqs_off(unsigned long a0, unsigned long a1)
{
        if (!preempt_trace() && irq_trace())
                start_critical_timing(a0, a1);
}

#else /* !CONFIG_PROVE_LOCKING */

/*
 * Stubs:
 */

void early_boot_irqs_off(void)
{
}

void early_boot_irqs_on(void)
{
}

void trace_softirqs_on(unsigned long ip)
{
}

void trace_softirqs_off(unsigned long ip)
{
}

inline void print_irqtrace_events(struct task_struct *curr)
{
}

/*
 * We are only interested in hardirq on/off events:
 */
void trace_hardirqs_on(void)
{
        if (!preempt_trace() && irq_trace())
                stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL(trace_hardirqs_on);

void trace_hardirqs_off(void)
{
        if (!preempt_trace() && irq_trace())
                start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL(trace_hardirqs_off);

void trace_hardirqs_on_caller(unsigned long caller_addr)
{
        if (!preempt_trace() && irq_trace())
                stop_critical_timing(CALLER_ADDR0, caller_addr);
}
EXPORT_SYMBOL(trace_hardirqs_on_caller);

void trace_hardirqs_off_caller(unsigned long caller_addr)
{
        if (!preempt_trace() && irq_trace())
                start_critical_timing(CALLER_ADDR0, caller_addr);
}
EXPORT_SYMBOL(trace_hardirqs_off_caller);

#endif /* CONFIG_PROVE_LOCKING */
#endif /*  CONFIG_IRQSOFF_TRACER */

#ifdef CONFIG_PREEMPT_TRACER
void trace_preempt_on(unsigned long a0, unsigned long a1)
{
        if (preempt_trace())
                stop_critical_timing(a0, a1);
}

void trace_preempt_off(unsigned long a0, unsigned long a1)
{
        if (preempt_trace())
                start_critical_timing(a0, a1);
}
#endif /* CONFIG_PREEMPT_TRACER */

static void start_irqsoff_tracer(struct trace_array *tr)
{
        register_ftrace_function(&trace_ops);
        if (tracing_is_enabled())
                tracer_enabled = 1;
        else
                tracer_enabled = 0;
}

static void stop_irqsoff_tracer(struct trace_array *tr)
{
        tracer_enabled = 0;
        unregister_ftrace_function(&trace_ops);
}

static void __irqsoff_tracer_init(struct trace_array *tr)
{
        save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
        trace_flags |= TRACE_ITER_LATENCY_FMT;

        tracing_max_latency = 0;
        irqsoff_trace = tr;
        /* make sure that the tracer is visible */
        smp_wmb();
        tracing_reset_online_cpus(tr);
        start_irqsoff_tracer(tr);
}

static void irqsoff_tracer_reset(struct trace_array *tr)
{
        stop_irqsoff_tracer(tr);

        if (!save_lat_flag)
                trace_flags &= ~TRACE_ITER_LATENCY_FMT;
}

static void irqsoff_tracer_start(struct trace_array *tr)
{
        tracer_enabled = 1;
}

static void irqsoff_tracer_stop(struct trace_array *tr)
{
        tracer_enabled = 0;
}

#ifdef CONFIG_IRQSOFF_TRACER
static int irqsoff_tracer_init(struct trace_array *tr)
{
        trace_type = TRACER_IRQS_OFF;

        __irqsoff_tracer_init(tr);
        return 0;
}
static struct tracer irqsoff_tracer __read_mostly =
{
        .name           = "irqsoff",
        .init           = irqsoff_tracer_init,
        .reset          = irqsoff_tracer_reset,
        .start          = irqsoff_tracer_start,
        .stop           = irqsoff_tracer_stop,
        .print_max      = 1,
#ifdef CONFIG_FTRACE_SELFTEST
        .selftest    = trace_selftest_startup_irqsoff,
#endif
};
# define register_irqsoff(trace) register_tracer(&trace)
#else
# define register_irqsoff(trace) do { } while (0)
#endif

#ifdef CONFIG_PREEMPT_TRACER
static int preemptoff_tracer_init(struct trace_array *tr)
{
        trace_type = TRACER_PREEMPT_OFF;

        __irqsoff_tracer_init(tr);
        return 0;
}

static struct tracer preemptoff_tracer __read_mostly =
{
        .name           = "preemptoff",
        .init           = preemptoff_tracer_init,
        .reset          = irqsoff_tracer_reset,
        .start          = irqsoff_tracer_start,
        .stop           = irqsoff_tracer_stop,
        .print_max      = 1,
#ifdef CONFIG_FTRACE_SELFTEST
        .selftest    = trace_selftest_startup_preemptoff,
#endif
};
# define register_preemptoff(trace) register_tracer(&trace)
#else
# define register_preemptoff(trace) do { } while (0)
#endif

#if defined(CONFIG_IRQSOFF_TRACER) && \
        defined(CONFIG_PREEMPT_TRACER)

static int preemptirqsoff_tracer_init(struct trace_array *tr)
{
        trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;

        __irqsoff_tracer_init(tr);
        return 0;
}

static struct tracer preemptirqsoff_tracer __read_mostly =
{
        .name           = "preemptirqsoff",
        .init           = preemptirqsoff_tracer_init,
        .reset          = irqsoff_tracer_reset,
        .start          = irqsoff_tracer_start,
        .stop           = irqsoff_tracer_stop,
        .print_max      = 1,
#ifdef CONFIG_FTRACE_SELFTEST
        .selftest    = trace_selftest_startup_preemptirqsoff,
#endif
};

# define register_preemptirqsoff(trace) register_tracer(&trace)
#else
# define register_preemptirqsoff(trace) do { } while (0)
#endif

__init static int init_irqsoff_tracer(void)
{
        register_irqsoff(irqsoff_tracer);
        register_preemptoff(preemptoff_tracer);
        register_preemptirqsoff(preemptirqsoff_tracer);

        return 0;
}
device_initcall(init_irqsoff_tracer);